Traveling wave tube having a helix delay line

Abstract

A traveling wave tube has a helical delay line which is supported by a plurality of dielectric support rods extending along the delay line. The delay line and support rods are housed within a metallic sleeve which has an enlarged diameter in the area of each end of the delay line. In this area at each end of the delay line a respective coupling conductor is connected to the delay line for supplying and discharging HF energy. In order to achieve a low reflection transition between the surge impedance of the delay line and that of the coupling conductor, in the region of at least one of the two ends of the delay line, a metallic matching component is provided which is peferably spot welded to a surface formed at the diameter enlargement, the matching component including an arm which is spot welded to that surface and projections extending from the arm radially inwardly between adjacent support rods and in close proximity to the delay line. The end surfaces of the projections which face the delay line are darkened to absorb heat radiated by the delay line and discharge the same toward the exterior of the traveling wave tube.

I claim: 
     
       1. In a traveling wave tube of the type having a helical delay line supported by a plurality of dielectric rods within a metallic sleeve and having coupling conductors connected to respective ends of the delay line to supply and discharge HF energy, respectively, the improvement therein comprising: means for providing a low reflection transition between the delay line and at least one of the coupling conductors, including, in the area of at least one of the ends of the delay line, a metallic matching component comprising an arm connected to the metallic sleeve and projections extending from said arm and extending between the support rods and in close proximity to the delay line, said projections spaced a distance s from the delay line in accordance with the range relationship   0.02λ .sub.g < s< 0.15λ.sub.g        and extending a distance l in the direction of the axis of the delay line in accordance with the range relationship   0.1λ.sub. g < l< 0.3λ.sub.g        where λ g  is the short wave length of the delay line.   
     
     
       2. The improved traveling wave tube according to claim 1, wherein each of said projections includes a darkened end surface adjacent the delay line to absorb heat radiated from the delay line. 
     
     
       3. The improved traveling wave tube according to claim 1, wherein said arm is narrower in the direction of the longitudinal axis of the delay line than said projections. 
     
     
       4. The improved traveling wave tube according to claim 1, wherein said arm is arcuate and extends about the delay line less than 360°. 
     
     
       5. In an improved traveling wave tube according to claim 1, the further improvement wherein: the metallic sleeve includes a portion of increased diameter in the area of said one end of the delay line defining a surface normal to the longitudinal axis of the delay line, and   said arm is fixed to said surface.   
     
     
       6. In an improved traveling wave tube according to claim 5, the improvement is further defined wherein said arm includes a surface parallel to and abutting said surface which is defined by said increased diameter portion, and   said arm is spot welded to the latter-mentioned surface of the metallic sleeve.   
     
     
       7. The improved traveling wave tube according to claim 1, wherein each of said projections extend between and contact adjacent ones of the support rods. 
     
     
       8. A traveling wave tube comprising: a metallic sleeve including a first portion of a first inner diameter, at least one second portion of a greater second diameter and a surface at the junction of said first and second portions;   a electron beam generator in one end of said sleeve and an electron beam collector in the other end of said sleeve;   a delay line extending through said first portion;   input and output coupling conductors coupled to respective ends of said delay line for supplying and discharging HF energy; and   at least one metallic matching component in said second portion of said sleeve for matching the surge impedances of said delay line and the respective coupling conductor coupled to that end of said delay line, said component comprising an arm secured to said surface and projections extending toward and in close proximity to said delay line, said projections extending radially inwardly to a point in the range of 0.02-0.15 λ g  from the delay line and in the axial direction of said delay line a distance in the range of 0.1-0.3 λ g , where λ g  is the shortened wave length on said delay line.   
     
     
       9. The traveling wave tube of claim 8, wherein said projections extend a greater distance along the axial direction of said delay line than said arm. 
     
     
       10. The traveling wave tube of claim 8, wherein each of said coupling conductors comprises a coaxial line having an inner conductor and an outer conductor said inner conductor electrically connected to the respective end of said delay line and said outer conductor electrically connected to said matching component via said sleeve.   
     
     
       11. The traveling wave tube of claim 8, wherein said delay line is a helix, and   said matching component is arcuate shaped and partially surrounds the outermost turn of said delay line helix.   
     
     
       12. The traveling wave tube of claim 8, comprising: spot weld connections securing said arm of said matching component to said surface.   
     
     
       13. The traveling wave tube of claim 8, wherein said delay line generates heat and said projections each comprise: a darkened end surface facing said delay line to absorb heat radiated by said delay line.   
     
     
       14. The traveling wave tube of claim 8, wherein said delay line comprises: a helix having one end electrically connected to one of said coupling conductors and the other end electrically connected to the other of said coupling conductors; and   a plurality of dielectric support rods spaced about, extending along and supporting said helix, said projections extending between adjacent support rods.   
     
     
       15. The traveling wave tube of claim 14, wherein each of said projections contacts each of said support rods which are adjacent thereto. 
     
     
       16. The traveling wave tube of claim 14, wherein said support rods are spaced at 120° about said helix,   said coupling conductors extend radially outwardly of said sleeve at approximately 180° of one of said support rods, and   said one support rod is contacted and extends between two of said projections.   
     
     
       17. A traveling wave tube comprising: a metallic sleeve including a first portion of a first inner diameter, second and third portions each having a greater second inner diameter at opposite ends of said first portion, and first and second surfaces at the respective junctions of said first and second portions and said first and third portions, said surfaces extending perpendicular to the longitudinal axis of said sleeve;   an electron beam generator in said second portion and an electron beam collector in said third portion;   a coaxial input coupling for coupling in HF energy, including an inner conductor, and including an outer conductor electrically connected to said sleeve at said second portion;   a coaxial output coupling for coupling out HF energy, including an inner conductor, and including an outer conductor electrically connected to said sleeve and said third portion;   a helical delay line extending through said first portion and having opposite ends extending into said second and third portions, repectively, said ends electrically connected to respective inner conductors of said coaxial input and output couplings;   a plurality of dielectric support rods spaced about to support and extend along said helical delay line; and   a pair of metallic matching components at respective ends of said delay line for matching the surge impedance of said couplings and said delay line, each of said matching components comprising   an arm electrically connected and mechanically fixed to a respective one of said first and second surfaces, and   projections extending from said arm between adjacent ones of said support rods and in close proximity to said delay line, said projections extending to a point which is spaced from said delay line in the range of 0.02 to 0.15 λ g , and said projections extending in the axial direction a distance in the range of 0.1 to 0.3 λ g , where λ g  is the shortened wave length on said delay line.   
     
     
       18. The traveling wave tube of claim 17, comprising at least one conductor extending between and electrically connecting an inner coaxial conductor with the respective end of said helical delay line.   
     
     
       19. The traveling wave tube of claim 17, wherein each of said projections includes a darkened surface facing said delay line to absorb heat radiated by said delay line.   
     
     
       20. The traveling wave tube of claim 17, wherein each of said matching components is arcuate shaped and only partially surrounds the respective end of said helical delay line.   
     
     
       21. The traveling wave tube of claim 17, comprising: spot weld connections securing said arms of said matching components to the respective first and second surfaces.   
     
     
       22. The traveling wave tube of claim 17, wherein said plurality of dielectric support rods comprises three such rods spaced apart 120° about said helical delay line,   said projections comprises two such projections extending on each side of one of said support rods and contacting each of said support rods, and   the connections of said inner coaxial conductors and said delay line are at 180° with respect to said one support rod.   
     
     
       23. The improved traveling wave tube according to claim 1, wherein said matching component does not surround the outermost turn of said delay line helix. 
     
     
       24. The traveling wave tube of claim 8, wherein said matching component does not surround the outermost turn of said delay line helix.   
     
     
       25. The traveling wave tube of claim 17, wherein said matching component does not surround the outermost turn of said delay line helix.